In conventional processes for plating plastic substrates, a thin first layer of metal, such as copper or nickel, is chemically deposited over the surface of the substrate in an electroless plating process. The electrolessly deposited layer is then used as a buss to build up a thicker metal coating over the substrate in an electolytic plating process.
If it is desired that certain areas or surfaces of the part remain unplated, those surfaces must be masked at least during the electroless plating process. This can be done in various ways. For example, tape or some other adhesive can be applied to the surfaces which are not to be plated. Such a procedure, however, is generally limited to flat surfaces over which the tape can be applied. For more complex surfaces, a chemical resist is generally preferred.
Chemical resists are non-typically, non-conductive, non-platable material which can be applied to the surface of the plastic substrates as a liquid, for example by brush or spray painting techniques, and which, when dried, will resist plating, i.e., will not be plated, in the electroless plating process. That is, only the surfaces of the substrate which do not receive the resist will be plated. After the substrate has been plated, the resist can be stripped off, if desired, by an appropriate solvent.
While the use of non-platable chemical resists is effective, it is expensive. In addition to the cost of the chemical resist material itself, expense is incurred as a result of the time, effort and, in some instances, equipment required to apply the resist to the substrate. Accordingly, there is a need for a method for selectively plating plastic substrates without the use of chemical resists or other masks.